The term “heterodiamond” is conventionally defined to mean a super hard material containing boron, carbon and nitrogen (BCN). It is formed at high temperatures and high pressures, e.g., by application of an explosive shock wave to a mixture of diamond and cubic boron nitride.” In contrast, the heterodiamond of the present invention is produced using combinatorial synthesis reactions at or around ambient pressure. Furthermore, the heterodiamond of the present invention, synthesized controllably and with precise stoichiometry, can be exclusively either aza-diamond or bora-diamond. This is the definition and meaning of the term “heterodiamond” as used in the present specification, which is not to be confused with the conventionally used term “heterodiamond,” which is BCN as already noted.
In addition, the term “diamond molecule” has been incorrectly used for diamondoid molecules and masses of diamondoid molecules such as adamantine. In fact, adamantane is a hydrocarbon whose structure is unrelated to that of the diamond unit cell: the diamond molecule.
Zhao et al., in U.S. Pat. No. 7,938,997, disclose the preparation of a bulk superhard B—C—N nanocomposite compact. This is done by first ball-milling a mixture of graphite and hexagonal boron nitride, which is then encapsulated in a pressure range of 15 GPa to about 25 GPa and sintered at a temperature ranging from 1,800 to 2,500 K. These compacts include both boron and nitrogen. The heterodiamond of the present invention, however, is produced by a combinatorial synthesis reaction at generally ambient conditions. Furthermore, the present invention controllably yields either bora-diamond or aza-diamond individually with precise stoichiometries.
Popov et al. in their article “Deposition of BCN Films by Laser Ablation,” describe the deposition of BCN films on silicon substrates by laser ablation. The films were deposited at 600° C. and 950° C. In contrast, the present invention produces aza-diamond and bora-diamond with precise stoichiometries under generally ambient conditions using a combinatorial synthesis of heterodiamond unit cells.
Goglio et al. disclose the decomposition of commercial thiosemicarbazide at 600° C. under nitrogen flow to produce carbon nitrides. This is different from the present invention wherein a carbon of the diamond unit cell is substituted with a heteroatom to produce a heterodiamond unit cell using a combinatorial synthesis.
In the published patent application, US 2015/0240381, Linares et al. disclose a boron doped single crystal diamond electrochemical synthesis electrode. They dope diamond with boron and thus do not controllably and precisely introduce a boron atom as a heteroatom that substitutes for a carbon atom in the diamond unit cell. This is different from the present invention, which produces heterodiamond wherein a heteroatom becomes an integral atom in the unit cell, occupying either an apical position or center, “cage,” position of the unit cell.
The diamond unit cell is the smallest assembly of carbon atoms that make up diamond. It is, essentially, the diamond molecule. The diamond unit cell is a tetrahedral structure comprising five carbon atoms with a carbon atom at each of the four apices and one in the center, “cage” position. Each carbon atom is bonded to each other carbon atom of the diamond unit cell. The bonds in diamond are short, strong sp3 bonds, which render the three-dimensional, solid structure of diamond, as opposed to graphite, another allotrope of carbon, which has sp2 bonds and is planar. The preparation of the diamond unit cell, whose structure is shown below, is described in U.S. Pat. Nos. 8,778,295 and 9,061,917:

Conventional ways of fabricating diamond generally rely on the use of high pressure/high temperature or chemical vapor deposition methods. Diamond produced conventionally has several disadvantages including the following three. First, the high temperature processing of conventional methods precludes the use of many deposition substrates. Second, lengthy processing times make conventional diamond production uneconomical for many potential applications. Third, impurities produced by conventional methods require additional, expensive purification steps before the diamond product can be used in high precision applications such as semiconductor electronics and optics.
As a material, diamond has many desirable properties that make it ideal for microelectronic, optics, and other technological applications. These include extreme hardness, high index of refraction, high dielectric constant, extremely broad transparency bandwidth, band gap energy of around 5.45 ev, and others. Additionally, while diamond is an excellent electrical insulator, it is also one of the best heat conductors, more than four times better than copper. Unfortunately, because of their disadvantages, conventional methods of producing diamond have not been able to exploit these properties sufficiently to meet the large potential industrial demand that diamond, as a technological material, deserves. Furthermore, no method and apparatus to date has been able to produce reliably and controllably an identifiable diamond unit cell wherein a carbon atom is substituted by a heteroatom to produce “heterodiamond” as defined herein.
A diamond p-type semiconductor can be produced by doping diamond with boron. For example, when diamond is produced by conventional chemical deposition methods, boron is introduced into the gas stream of the reactor to form a boron impurity (i.e., dopant) that is incorporated into the diamond. This boron, however, is not controllably substituted for a carbon of the diamond unit cell, thus controllably and predictably yielding a heterodiamond unit cell. Rather, as an impurity, it is essentially a useful defect in the diamond crystal lattice.
It is also known that nitrogen can be contained within CVD-produced diamond. Indeed, nitrogen vacancies in diamond are currently an active area of research because they have the potential to yield a spintronic material that can be used as quantum electronic devices with qubits and quantum logic gates. This work is described in an article titled “The Diamond Age of Spintronics” (David D. Awschalom, et al., Scientific American, October, 2007, pp. 84-91.) The nitrogen of nitrogen vacancies in diamond and nitrogen-doped diamond, however, do not reliably and controllably substitute for a carbon atom of the diamond unit cell to yield a heterodiamond unit cell.
The term “heterodiamond” has been used conventionally, albeit incorrectly, for a very hard material containing boron, carbon and nitrogen (BCN) usually formed by applying a shock wave to a mixture of diamond and cubic boron nitride. Another variety is cubic BC2N, which is produced at very high pressures from a graphite-like BC2N. Thus, heterodiamond has been used conventionally to describe a ceramic material, which is not structurally related to diamond. These ceramic materials do not reliably, controllably, and consistently comprise a diamond unit cell that has been modified to include a heteroatom such as boron or nitrogen substituting for a carbon atom of the diamond unit cell to produce a heterodiamond unit cell. In contrast the present invention is directed to a diamond unit cell having a carbon replaced by a single heteroatom such as nitrogen or boron resulting in a heterodiamond unit cell. Thus, for the purposes of this specification, the term “heterodiamond” is used to mean a material comprising at least one diamond unit cell wherein a heteroatom, such as nitrogen or boron, replaces a carbon atom: the heterodiamond unit cell. For the purposed of the present invention, the homo-penta-atomic molecule having five carbon atoms in a tetrahedral configuration with one carbon atom occupying the center “cage” position and four carbon atoms deployed apically, is designated the “homodiamond unit cell.”
It is important to distinguish between the use of boron and nitrogen as diamond dopants and the use of those elements in the present invention wherein nitrogen and boron are incorporated as structural members of the diamond unit cell. When nitrogen, boron, or other elements are used as diamond dopants, they are infiltrated into the lattice of the diamond mass. They are not chemically a part of the structure of the diamond unit cell in that they are not bonded to the carbon atoms that comprise the diamond unit cell. They are, rather, intervening impurities that become defects in the diamond crystal lattice that render the diamond a semiconductor. In contrast to doped diamond, the heteroatoms of the present invention are structurally a part of the crystal lattice because they are structural elements of the heterodiamond unit cells and of the heterodiamond mass which they comprise.
A heteroatom can occupy one of two positions of the heterodiamond unit cell, the center “cage” position or an apex position of the tetrahedron. A geometric analysis can be performed relating to atoms with sizes that are close to that of carbon. In the periodic chart, carbon is flanked by the III, V elements boron and nitrogen, respectively. Carbon has an atomic radius of 70 pm, while boron and nitrogen have atomic radii of 85 pm and 65 pm, respectively. The covalent radii of carbon, boron and nitrogen, are 77 pm, 83 pm, and 75 pm, respectively. Thus, the practitioner will recognize that nitrogen is small enough to occupy the center “cage” position of the diamond unit cell. The atomic radius and covalent radius of boron are such that it can occupy an apical position of the heterodiamond unit cell.
Thus, the skilled practitioner might recognize that boron or nitrogen as a substitute element for carbon in a diamond unit cell is possible if a mechanism for their incorporation could be implemented. Heterodiamond unit cells, which are the subject of the present invention, include aza-diamond, in which the heteroatom is nitrogen, and bora-diamond, in which the heteroatom is boron. These are shown below:

The skilled practitioner will also recognize that aza-diamond and bora-diamond, once formed, are charged monopoles, that is, species bearing charge with no counter charge.

However, to date, neither of the above compounds have been formed, let alone used to form masses of aza-diamond and bora-diamond.